It is conventionally known that the causes of ischemic disorders of organs are broadly divided into poor blood circulation and functional impairment of organs themselves. For example, stenosis, which is an example of poor blood circulation of the coronary artery, is a significant lesion that causes ischemic heart diseases, and there is a need to determine whether drug treatment is to be conducted, whether stent treatment is to be conducted, or the like, for the ischemic heart diseases. In recent years, for diagnosis that conducts evaluation of hematogenous ischemia in the coronary artery, there has been a suggested technique for measuring Fractional Flow Reserve (FFR) by using a pressure wire during coronary artery contrast examination (coronary angiography: CAG) using a catheter.
The FFR is the index for assuming how much blood flow is disturbed by a lesion, such as stenosis, and it is defined by using the ratio of the flow volume in a case where there is no lesion to the flow volume in a case where there is a lesion. Here, during the actual FFR measurement, the measurement is conducted by replacing the flow volume within a blood vessel with the pressure. For example, during the FFR measurement, adenosine is administered to obtain the maximum engorged state (blood-vessel expanded state) so that the relationship between the flow volume and the pressure within a blood vessel is a proportional relationship, and the flow volume that defines the FFR is replaced with the pressure. Thus, the FFR may be measured on the basis of the pressure within a blood vessel, measured by using the above-described pressure wire.
furthermore, in recent years, there has been a known technique for conducting FFR measurement without administering the above-described adenosine. According to the above-described technique that uses adenosine, adenosine is administered so that the relationship between the flow volume and the pressure within s blood vessel becomes a proportional relationship and the pressure within the blood vessel is measured; however, in the case of the technique that is conducted without administering adenosine, the pressure is measured in the time phase where the relationship between the flow volume and the pressure within a blood vessel in a resting state is a proportional relationship. Specifically, as the relationship between the flow volume and the pressure within a blood vessel is a proportional relationship even in a resting state during the wave-free period (the period in which the vascular resistance is smaller and stable) in the cardiac cycle, the FFR is measured on the basis of the pressure that is measured by using a pressure wire during the wave-free period according to the technique that is conducted without administering adenosine.
As described above, the FFR measurement is conducted by using a pressure wire for diagnosis that conducts evaluation of hematogenous ischemia in the coronary artery; however, contrary to the above-described FFR measurement, that uses a pressure wire, in recent years, there has been a known technique for conducting evaluation of hematogenous ischemia in the coronary artery in a non-invasive manner by using medical images of the heart, collected by medical-image diagnostic apparatus, such as X-ray computed tomography (CT) apparatus, magnetic resonance imaging (MRI) apparatus, or ultrasonic diagnostic apparatus. Recently, hematogenous ischemia evaluation has been conducted by using the above-described various techniques, and treatments are given in according to the evaluation.